Modern motor vehicles are equipped with numerous sensors that provide detailed information regarding the operation of the vehicle. This information may be displayed for a driver or it may be processed and provided to various vehicle control systems. A target wheel sensor, for example, may be used to determine the angular speed or angular position of a rotating object in the vehicle, e.g., a crankshaft and a driveshaft. In either case, a target wheel may be engaged with the rotating object for inducing signals in one or more sensors positioned next to the target wheel, with the signals representing the angular position or angular speed of the rotating object. These signals can be used in various control systems, e.g., an ignition system and a speed control system. The present invention recognizes that certain applications require the detection of not only the position of the object, but the detection of the direction of motion of the rotating object as well.
U.S. patent application Ser. No. 09/777,764 titled “Target Wheel Sensor Assembly For Determining Position And Direction Of Motion Of A Rotating Target Wheel”, commonly assigned to the same assignee of the present invention and herein incorporated by reference, in part teaches how detection of direction of rotation can be obtained from an asymmetric sensor. This application focuses on designs with “one and only one sensing element”. Using a single sensing element should conceptually provide a low-cost solution. In practice, however, dual sensors (e.g., Hall sensors) used in a differential mode are at the present time, essentially a commodity. Therefore, at least under the present state of affairs regarding sensor technology, dual sensors may actually constitute the lower cost solution.
In view of the foregoing, it would be desirable to extend the innovative concepts of U.S. patent application Ser. No. 09/777,764 to a sensor assembly using differential sensors (more generally, two or more sensing elements).